1. Field of the Invention
The present invention relates to a gas circulation type laser oscillator which is mounted in a laser processing machine which is mainly used for cutting, welding, etc. of metal materials and plastic materials etc., and is configured to generate laser by excitation discharge of a laser gas flow through the inside of a discharge tube.
2. Description of the Related Art
Laser oscillators which generate laser by excitation discharge of a mixed gas circulating through a ring-shaped blower path are widely used. Such a laser oscillator is called a “gas circulation type laser oscillator”. In a gas circulation type laser oscillator, dust or particulate matter which enters the blower path during assembly, and a foreign substance such as quartz powder which is produced during excitation discharge due to abrasion of the inner wall of a discharge tube made from quarts may also circulate inside the blower path together with the mixed gas. Furthermore, an oxidation reaction of ozone which is produced during excitation discharge of the mixed gas may also cause formation of various oxides. If these foreign matters adhere to a partial reflector or total reflector or other optical components, the output power of the laser will reduce, and it may create a need to clean or replace the optical components. In relation to this, JPH05-167131A proposes a gas laser oscillator in which a protective cover which doubly serves as a blower guide of the laser gas is arranged near a support rod which connects an output side resonator and a rear side resonator so as to minimize the thermal impact on the support rod due to high temperature laser gas.
Further, JP2003-110171A proposes a laser oscillator which employs a plurality of slit-shaped laser gas introduction ports which are arranged on the same circumference so as to prevent turbulence which can occur near the laser gas introduction ports, and entrainment of electrode powder and other foreign matter due to the turbulence. Furthermore, the laser oscillator of JP2003-110171A is structured so that the laser gas introduction ports are arranged near the reflection mirrors, and raises the gas pressure of the laser gas which is supplied from the laser gas introduction ports to the reflection mirrors so as to prevent impurities produced in a laser resonating cavity from scattering to the reflection mirrors. However, according to the structure of the laser oscillator of JP2003-110171A, foreign matter which had adhered to the inside wall of the feed piping of the laser gas may be discharged near the reflection mirrors, and therefore the reflection mirrors may be contaminated further due to that foreign matter. Further, JPH05-102575A proposes a laser oscillator which employs a plate type heat exchanger which is expected to facilitate the removal of dust produced during the manufacturing process. However, the laser oscillator of JPH05-102575A can only prevent mixing of the foreign matter in the heat exchanger into the blower path during the time of assembly, and cannot prevent contamination of the optical components due to foreign matter which is produced due to excitation discharge of the laser gas.
A gas circulation type laser oscillator which can prevent dust mixed in the laser gas from adhering to the optical components is being sought.